Why are my signs different?

They come from three different traditions that measure the sky in different ways:

Western (tropical): the system most of the world knows. It ties the zodiac to the seasons — 0° Aries is the spring equinox. This is your familiar Sun sign.
Vedic (sidereal / Jyotish): the traditional astrology of India. It ties the zodiac to the actual constellations. Because of a slow wobble in Earth's axis, the two zodiacs have drifted about one sign apart, so your Vedic Sun is usually one sign back. Vedic also weighs your Moon sign and Nakshatra heavily — see the Vedic calculator.
Chinese: a completely separate system — a 12-year cycle of animals tied to the lunar calendar, combined with the five elements. See Chinese astrology.

So which one is "right"?

None is more "correct" than the others — they're different lenses, and many people feel that one describes them better than the rest. That's half the fun. Read your Western sign profile, compare it to the Vedic reading, and trust what resonates.

For reflection and interest only. AstrologyBay presents astrology as an interest-and-belief framework, not a scientific claim.